Oxygenator with integrated arterial filter including filter frame

ABSTRACT

An oxygenator combines, in a single structure, a heat exchanger, a gas exchanger, an arterial filter, and a filter frame. Such an oxygenator permits fewer fluid connections and thus may simplify an extracorporeal blood circuit, including a heart-lung machine and a blood reservoir, in which it is used. In some embodiments, the oxygenator may be configured to include multiple purge ports for purging bubbles both before and after filtering the blood.

RELATED APPLICATION

This application is a continuation-in-part of U.S. application Ser. No.12/770,327 filed Apr. 29, 2010, entitled “Oxygenator with IntegratedArterial Filter,” which is hereby incorporated by reference. Thisapplication also claims priority to European Application No. 10186550.9,filed Oct. 5, 2010, entitled “Oxygenator with Integrated Arterial FilterIncluding Filter Frame,” which is hereby incorporated by referenceherein in their entirety.

TECHNICAL FIELD

The disclosure pertains generally to arterial filters used in bloodperfusion systems.

BACKGROUND

Blood perfusion entails encouraging blood through the vessels of thebody. For such purposes, blood perfusion systems typically entail theuse of one or more pumps in an extracorporeal circuit that isinterconnected with the vascular system of a patient. Cardiopulmonarybypass surgery typically requires a perfusion system that provides forthe temporary cessation of the heart to create a still operating fieldby replacing the function of the heart and lungs. Such isolation allowsfor the surgical correction of vascular stenosis, valvular disorders,and congenital heart defects. In perfusion systems used forcardiopulmonary bypass surgery, an extracorporeal blood circuit isestablished that includes at least one pump and an oxygenation device toreplace the functions of the heart and lungs.

More specifically, in cardiopulmonary bypass procedures oxygen-poorblood, i.e., venous blood, is gravity-drained or vacuum suctioned from alarge vein entering the heart or other veins in the body (e.g., femoral)and is transferred through a venous line in the extracorporeal circuit.The venous blood is pumped to an oxygenator that provides for oxygentransfer to the blood. Oxygen may be introduced into the blood bytransfer across a membrane or, less frequently, by bubbling oxygenthrough the blood. Concurrently, carbon dioxide is removed across themembrane. The oxygenated blood is filtered and then returned through anarterial line to the aorta, femoral, or other artery.

Often, an arterial filter is added to the extracorporeal circuit, afterthe oxygenator, as last barrier before the patient, so as to block anysolid or gaseous emboli and prevent any such emboli from entering intothe aorta of the patient. Recently, arterial filters integrated in theoxygenator have been developed, allowing the reduction of the primingvolume of the circuit and decreasing the global haemodilution of thepatient.

SUMMARY

Example 1 is a blood processing apparatus that includes an apparatushousing having a blood inlet and a blood outlet, the blood inlet extendsinto an interior of the apparatus housing. A heat exchanger is disposedabout the blood inlet and in fluid communication therewith. A gasexchanger is disposed about the heat exchanger and in fluidcommunication therewith. A filter housing is coupled about the apparatushousing and defining a filter volume between the apparatus housing andthe filter housing, the filter volume is in fluid communication with thegas exchanger via one or more openings that are formed within theapparatus housing such that blood exiting the gas exchanger can passinto the filter volume. A filter assembly is disposed within the filterhousing. The filter assembly includes a filter frame having one or moreribs and a filter net disposed on the filter frame. The one or more ribsalign with at least a portion of the one or more openings so as toreduce blood velocity through at least a portion of the filter net.

In Example 2, the blood processing apparatus of Example 1 in which oneor more openings comprise a plurality of openings arranged along anarcuate path. The one or more ribs comprise arcuate ribs aligned withthe arcuate path.

In Example 3, the blood processing apparatus of Example 1 in which thefilter frame has a first annular frame ring having a first diameter, asecond annular frame ring having a second diameter, greater than thefirst diameter, and one or more bridge elements extending between thefirst annular frame ring and the second annular frame ring.

In Example 4, the blood processing apparatus of Example 3 in which oneor more ribs are disposed between the first annular frame ring and thesecond annular frame ring.

In Example 5, the blood processing apparatus of Example 1 in which thefilter frame includes a plate portion arranged near the blood outlet tolimit preferential blood flow through the filter assembly near the bloodoutlet.

In Example 6, the blood processing apparatus of Example 1 in which thefilter assembly divides the filter volume into a first chamber betweenthe filter assembly and the apparatus housing and a second chamberbetween the filter assembly and the filter housing.

In Example 7, the blood processing apparatus of Example 6, in whichfurther comprises a first purge port in fluid communication with thefirst chamber and a second purge port in fluid communication with thesecond chamber.

In Example 8, the blood processing apparatus of Example 7 in which thefilter housing has a frustoconical configuration having a smallerdiameter at one end and a larger diameter at an opposing end. The secondpurge port is located near the larger diameter end of the filterhousing.

In Example 9, the blood processing apparatus of Example 8 in which thefirst purge port is located near the smaller diameter end of the filterhousing.

In Example 10, the blood processing apparatus of Example 7 in whichbubbles within the blood can exit through the first purge port and/orthe second purge port.

In Example 11, the blood processing apparatus of Example 1 in which thegas exchanger is configured to permit gas to flow therethrough in orderto add oxygen and remove carbon dioxide from the blood passing throughthe gas exchanger.

In Example 12, the blood processing apparatus of Example 1 in which thefilter assembly includes a biocompatible coating on the filter net.

In Example 13, the blood processing apparatus of Example 1 in which thefilter net comprises a polyester filter net or a polypropylene filternet.

Example 14 is a blood processing apparatus that includes an apparatushousing having a blood inlet and a blood outlet, the blood inletextending into an interior of the apparatus housing. A heat exchangercore extends coaxially within the apparatus housing and is axiallyaligned with the blood inlet. Heat exchanger hollow fibers are disposedabout the heat exchanger core such that a heat exchanger fluid may flowthrough the heat exchanger hollow fibers and blood passing from theblood inlet may flow across the heat exchanger hollow fibers. Acylindrical shell extends coaxially about the heat exchanger core. Thecylindrical shell includes an annular shell aperture that is disposednear an end of the cylindrical shell opposite to an end near the bloodinlet. The annular shell aperture is configured to permit blood to passto an exterior of the cylindrical shell. Gas exchanger hollow fibers aredisposed about the cylindrical shell such that gases may flow throughthe gas exchanger hollow fibers and blood passing from the annular shellaperture may flow across the gas exchanger hollow fibers. A filterhousing is coupled about the apparatus housing and defines a filtervolume between the apparatus housing and the filter housing. The filtervolume is in fluid communication with the gas exchanger via one or moreopenings that are formed within the apparatus housing along an arcuatepath such that blood exiting the gas exchanger can pass into the filtervolume. A filter assembly is disposed within the filter housing anddivides the filter volume into a first chamber between the filterassembly and the apparatus housing and a second chamber between thefilter assembly and the filter housing. The filter assembly includes afilter frame with one or more arcuate ribs and a filter net disposed onthe filter frame. The one or more arcuate ribs are aligned with the oneor more openings along the arcuate path in order to slow blood velocitythrough the filter net. The blood processing apparatus includes a firstpurge port that is in fluid communication with the first chamber and asecond purge port that is in fluid communication with the secondchamber.

In Example 15, the blood processing apparatus of Example 14 in which thefilter assembly includes a biocompatible coating on the filter net.

In Example 16, the blood processing apparatus of Example 14 in which thefilter net comprises a polyester filter net or a polypropylene filternet.

While multiple embodiments are disclosed, still other embodiments of thepresent invention will become apparent to those skilled in the art fromthe following detailed description, which shows and describesillustrative embodiments of the invention. Accordingly, the drawings anddetailed description are to be regarded as illustrative in nature andnot restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a blood processing apparatusincluding an integrated arterial filter in accordance with an embodimentof the invention.

FIG. 2 is a cross-sectional illustration of the blood processingapparatus of FIG. 1.

FIG. 3 is an illustrative view of a filter deployed within the bloodprocessing apparatus of FIG. 1.

FIG. 4 is an illustrative view of another filter deployed within theblood processing apparatus of FIG. 1.

FIG. 5 is a schematic illustration of a blood processing apparatusincluding an integrated arterial filter in accordance with an embodimentof the invention.

FIG. 6 is a schematic cross-sectional illustration of the bloodprocessing apparatus of FIG. 5.

FIG. 7 is an illustrative view of a filter deployed within the bloodprocessing apparatus of FIG. 5.

FIG. 8 is a schematic illustration of a blood processing apparatusincluding an integrated arterial filter in accordance with an embodimentof the invention.

FIG. 9 is a perspective illustration of a blood processing apparatusincluding an integrated arterial filter in accordance with an embodimentof the invention.

FIG. 10 is a cross-sectional view of the blood processing apparatus ofFIG. 9.

FIG. 11 is a perspective illustration of a portion of the bloodprocessing apparatus of FIG. 9.

FIG. 12 is a perspective illustration of a portion of the bloodprocessing apparatus of FIG. 9.

FIGS. 13 and 14 are schematic illustrations of blood flow showing howblood flow velocity is reduced in the blood processing apparatus of FIG.9.

FIGS. 15 and 16 are graphical representations illustrating how backflowis reduced in the blood processing apparatus of FIG. 9.

DETAILED DESCRIPTION

The disclosure pertains to a blood processing apparatus that combines,in a single structure, a heat exchanger, a gas exchanger or oxygenatorand an arterial filter. In some embodiments, the term oxygenator may beused to refer to a structure that combines a heat exchanger, a gasexchanger and an arterial filter in a unitary device. In someembodiments, an oxygenator may be used in an extracorporeal bloodcircuit. An extracorporeal blood circuit, such as may be used in abypass procedure, may include several different elements such as aheart-lung machine, a blood reservoir, as well as an oxygenator. In someembodiments, by incorporating the arterial filter with the oxygenator,the tubing set used to create the extracorporeal blood circuit may bereduced in complexity or number of parts and thus may simplify theextracorporeal blood circuit. In some embodiments, this will reduce thepriming volume of the extracorporeal blood circuit.

FIG. 1 is a schematic illustration of a blood processing apparatus oroxygenator 10. While the internal components are not visible in thisillustration, the oxygenator 10 may include one or more of a heatexchanger, a gas exchanger and an arterial filter. According to someembodiments, each of the heat exchanger, gas exchanger and arterialfilter are integrated into a single structure that forms an oxygenatorhousing. The oxygenator 10 includes a device compartment or housing 12and an arterial filter compartment or housing 14. In some embodiments,the arterial filter housing 14 may be integrally molded or otherwisestructurally integrated with the device housing 12. In some cases, thearterial filter housing 14 may be separately formed and then secured orotherwise coupled to the device housing 12. According to variousembodiments, the heat exchanger, the gas exchanger, and the arterialfilter housing 14 may have a cross-section shaped generally as a circleor as a parallelogram (e.g., a square or rectangle). Each of the heatexchanger, the gas exchanger and the arterial filter housing 14 may havegenerally the same sectional shape or each may have a differentsectional shape.

In some embodiments, a blood inlet 16 extends through the arterialfilter housing 14 and into the device housing 12. A blood outlet 18exits the arterial filter housing 14. As noted, in some embodiments theoxygenator 10 includes a gas exchanger and thus may include a gas inlet20 and a gas outlet 22. In some embodiments, the oxygenator 10 includesa heat exchanger and thus may include a heating fluid inlet 24 and aheating fluid outlet 26. As will be explained in greater detail withrespect to FIG. 2, the oxygenator 10 includes a first purge port 28 anda second purge port 30. The positions of the inlets, outlets and purgeports are merely illustrative, as other arrangements and configurationsare contemplated. The purge ports may include a valve or a threaded cap.The purge ports operate to permit gases (e.g., air bubbles) that exitthe blood to be vented or aspirated and removed from the oxygenator.

FIG. 2 is a cross-sectional view of the oxygenator 10, illustratinginternal components and exemplary blood flow through the oxygenator 10.The oxygenator 10 includes a heat exchanger 32 and a gas exchanger 34.In some embodiments, the heat exchanger 32 includes a number of hollowfibers through which a heating fluid such as water can flow. The bloodmay flow around and past the hollow fibers and thus be suitably heated.In some embodiments, the hollow fibers may be polymeric. In some cases,metallic fibers may be used within the heat exchanger 32. According toother embodiments, the heat exchanger 32 includes a metal bellows orother structure comprising a substantial surface area (e.g., fins) forfacilitating heat transfer with the blood.

In some embodiments the gas exchanger 34 may include a number ofmicroporous hollow fibers through which a gas such as oxygen may flow.The blood may flow around and past the hollow fibers. Due toconcentration gradients, oxygen may diffuse through the hollow fibersinto the blood while carbon dioxide may diffuse into the hollow fibersand out of the blood.

The oxygenator 10, according to some embodiments, includes an annularspace 36 into which blood may flow as the blood exits the gas exchanger34. As illustrated, the annular space 36 may extend into the arterialfilter housing 14. According to exemplary embodiments, the annular space36 may be generally circular or generally rectangular. The arterialfilter housing 14 includes a filter 38. In some embodiments, the filter38 includes an annular frame 40 and a net or mesh 42 spanning theannular frame 40. In some embodiments, the filter 38 may be consideredas dividing a volume within the arterial filter housing 14 into a firstchamber 44 and a second chamber 46. In various embodiments, the annularframe 40 and the net or mesh 42 are disposed concentrically with respectto the filter housing 14. In other embodiments the annular frame 40 andthe mesh 42 are disposed about the housing 14 in a non-concentricmanner. According to exemplary embodiments, the internal (i.e., priming)volume of the arterial filter housing 14 is between about 30 to about150 mL or from about 80 and about 110 mL. According to otherembodiments, the priming volume is between about 30 to 150 mL or fromabout 90 and about 100 mL.

In some embodiments, the annular space 36 may open into or otherwise bein fluid communication with the first chamber 44. While blood is in thefirst chamber 44, any air bubbles that are present within the blood maybe vented through the second purge port 30. Blood may pass through thefilter 38 and into the second chamber 46. Any bubbles remaining in theblood, or caused by passage through the filter 38, may be vented throughthe first purge port 28. Blood may then exit the oxygenator 10 throughthe blood outlet 18. The presence of the first purge port 28 in thesecond chamber 46 and the second purge port 30 in the first chamber 44,according to various embodiments, will improve the priming speed due tothe fact that bubbles present in the blood have both a first and asecond opportunity to exit through a purge port. Moreover, in theseembodiments, the efficacy of the bubble or gas removal is improved,again due to the fact that bubbles present in the blood have both afirst and a second opportunity to exit through a purge port.

FIG. 3 is a view of the filter 38, illustrating the frame 40 and the netor mesh 42. FIG. 4 shows an embodiment of the filter 38 including ablocking plate 100. In some embodiments, the blocking plate 100 may besized, shaped and positioned near the blood outlet 18 to limitpreferential blood flow on the lower portion of the oxygenator 10.According to various embodiments, the filter 38 may have across-sectional shape that is circular, rectangular, or any other shape.

In some embodiments, the net or mesh 42 may have a mesh size that is therange of about 20 to about 200 microns. In some cases, the net or mesh42 may have a mesh size of about 120 microns. In some instances, the netor mesh 42 may have a mesh size of from about 38-40 microns, and may beformed of a polymeric material such as polyester or polypropylene. Insome cases, the net 42 may be coated with a biocompatible material. Theblocking plate 100 may be formed of any suitable material. In someembodiments, the blocking plate 100 may be integrally formed with theframe 40. According to various exemplary embodiments, the net or mesh 42has a surface area of between about 70 and about 90 square centimeters.According to other exemplary embodiments, the net or mesh 42 has asurface are of between about 75 and about 80 square centimeters.

FIG. 5 is a schematic illustration of a blood processing apparatus oroxygenator 110. While the internal components are not visible in thisillustration, the oxygenator 110 may include one or more of a heatexchanger, a gas exchanger and an arterial filter. The oxygenator 110includes a device housing 112 and an arterial filter housing 114. Insome embodiments, the arterial filter housing 114 may be integrallymolded or otherwise formed with the device housing 112. In some cases,the arterial filter housing 114 may be separately formed and thensecured to the device housing 112.

In some embodiments, a blood inlet 116 extends through the arterialfilter housing 114 and into the device housing 112. A blood outlet 118exits the arterial filter housing 114. As noted, in some embodiments theoxygenator 110 includes a gas exchanger and thus may include a gas inlet120 and a gas outlet 122. In some embodiments, the oxygenator 110includes a heat exchanger and thus may include a heating fluid inlet 124and a heating fluid outlet 126. As will be explained in greater detailwith respect to FIG. 6, the oxygenator 110 includes a first purge port128 and a second purge port 130. The positions of the inlets, outletsand purge ports are merely illustrative, as other arrangements andconfigurations are contemplated.

FIG. 6 is a cross-sectional view of the oxygenator 110, illustratinginternal components of the oxygenator 110. The oxygenator 110 includes aheat exchanger 132 and a gas exchanger 134. In some embodiments, theheat exchanger 132 includes a number of hollow polymeric or metallicfibers through which a heating fluid such as water can flow. The bloodmay flow around and past the hollow fibers and thus be suitably heated.In some embodiments the gas exchanger 134 may include a number of hollowfibers through which a gas such as oxygen may flow. The blood may flowaround and past the hollow fibers. Due to concentration gradients,oxygen may diffuse through the hollow fibers into the blood while carbondioxide may diffuse into the hollow fibers and out of the blood.

As shown in FIG. 6, the gas exchanger is configured such that bloodflows radially across the gas exchanger 134. In these embodiments, theoxygenator 110 includes an annular space 136 into which blood may flowas the blood exits the gas exchanger 134. According to variousembodiments, the annular space 136 may be either open or it may bepartially or completely filled with hollow fibers. As illustrated, thearterial filter housing 114 may extend over a portion of the annularspace 136. According to other embodiments, the gas exchanger 134, theheat exchanger 132, or both may be configured such that blood isdirected in a longitudinal flow path. In various exemplary embodimentswhere the gas exchanger 134 is configured such that blood flows in alongitudinal path, the annular space 136 is omitted. In theseembodiments, the blood flows out of the gas exchanger 134 near an endand flows directly into the arterial filter housing 114. In someembodiments, the opening between the gas exchanger 134 and the arterialfilter housing 114 is blocked or occluded at the radial locationcorresponding to the blood outlet 118 of the arterial filter housing114, to minimize or prevent direct flow from the gas exchanger 134 intothe blood outlet 118.

A filter 138 may be disposed within the arterial filter housing 114. Insome instances, as illustrated, the filter 138 divides the space withinthe annular filter housing 114 into a first chamber 144 and a secondchamber 146. An opening 148 that may extend circumferentially up toabout 360 degrees provides fluid communication between the annular space136 and the first chamber 144. While blood is in the first chamber 144,any air bubbles that are present within the blood may be vented throughthe first purge port 128. Blood may pass through the filter 138 and intothe second chamber 146. Any bubbles remaining in the blood, or caused bypassage through the filter 138, may be vented through the second purgeport 130. Blood may then exit the oxygenator 110 through the bloodoutlet 118.

FIG. 7 is a view of the filter 138. In some embodiments, the filter 138is a cylindrical filter that includes one or more reinforcements 140 anda cylindrical net or mesh 142. In some embodiments, the one or morereinforcements 140 may be molded into the cylindrical net or mesh 142.In some cases, the one or more reinforcements 140 may be adhesivelysecured to the cylindrical net or mesh 142. In some embodiments, the oneor more reinforcements 140 may extend cylindrically about the filter138. In some instances, the one or more reinforcements 140 may runacross the filter 138.

In some embodiments, the net or mesh 142 may have a mesh size that isthe range of about 20 to about 200 microns. In some cases, the net ormesh 142 may have a mesh size of about 120 microns. In some instances,the net or mesh 142 may have a mesh size of about 40 microns, and may beformed of a polymeric material such as polyester or polypropylene. Insome cases, the net 142 may be coated with a biocompatible material.

In some embodiments, the net or mesh 142 may include a blocking regionor plate 200 that is sized, shaped and positioned near the blood outlet118 to limit preferential blood flow on the lower portion of theoxygenator 110. The blocking plate 200 may be formed of any suitablematerial. In some embodiments, the blocking plate 200 may be molded orotherwise formed within the net or mesh 142.

FIG. 8 is a schematic illustration of a blood processing apparatus oroxygenator 310. While the internal components are not visible in thisillustration, the oxygenator 310 may include one or more of a heatexchanger, a gas exchanger and an arterial filter. The oxygenatorincludes a device housing 312 and an arterial filter housing 314. In theillustrated embodiment, the arterial filter housing 314 is integratedinto an end or side face of the device housing 312 and is configuredsuch that blood exiting the device housing 312 enters the arterialfilter housing 314. The device housing 312 includes a blood inlet 316while the arterial filter housing 314 includes a blood outlet 318.

In some embodiments, as illustrated, the arterial filter housing 314includes a net filter 320, a first purge port 322 and a second purgeport 324. The first purge port 322 may be in fluid communication with aninterior of the arterial filter housing 314 at a position upstream ofthe net filter 320 while the second purge port 324 may be in fluidcommunication with an interior of the arterial filter housing 314 at aposition downstream of the net filter 320. As described in more detailabove, this configuration allows an improvement and priming speed andefficacy, while also reducing the overall priming volume.

FIG. 9 is a schematic illustration of a blood processing apparatus 410.While the internal components are not visible in this illustration, theblood processing apparatus 410 may include one or more of a heatexchanger, a gas exchanger and an arterial filter. According to someembodiments, each of the heat exchanger, gas exchanger and arterialfilter are integrated into a single structure. The blood processingapparatus 410 includes an apparatus housing 412 and a filter housing414. In some embodiments, the filter housing 414 may be integrallymolded or otherwise structurally integrated with the apparatus housing412. In some cases, the filter housing 414 may be separately formed andthen secured or otherwise coupled to the apparatus housing 412. In someembodiments, as illustrated, the filter housing 414 may be considered ashaving a tapered or frustoconical shape.

In some embodiments, a blood inlet 416 extends through the filterhousing 414 and into the apparatus housing 412. A blood outlet 418 exitsthe filter housing 414. As noted, in some embodiments the bloodprocessing apparatus 410 includes a gas exchanger and thus may include agas inlet 420 and a gas outlet 422. In some embodiments, the bloodprocessing apparatus 410 includes a heat exchanger and thus may includea heating fluid inlet 424 and a heating fluid outlet 426. In someembodiments, the blood processing apparatus 410 may include a firstpurge port 428 and a second purge port 430. The positions of the inlets,outlets and purge ports are merely illustrative, as other arrangementsand configurations are contemplated. The purge ports may include a valveor a threaded cap. The purge ports operate to permit gases (e.g., airbubbles) that exit the blood to be vented or aspirated and removed fromthe blood processing apparatus 410.

FIGS. 10, 11 and 12 further illustrate portions of the blood processingapparatus 410. FIG. 10 is a cross-sectional view of the blood processingapparatus 410, while FIGS. 11 and 12 are perspective views with someelements or features removed to illustrate underlying structure.

The blood processing apparatus 410 includes a heat exchanger 432 and agas exchanger 434. In some embodiments, the heat exchanger 432 includesa heat exchanger core 440 including a blood diverter end 442 that isconfigured to divert blood exiting the blood inlet 416 past hollowfibers 444 through which a heating fluid (e.g., water) can flow. Theblood may flow around and past the hollow fibers 444 and thus besuitably heated (or cooled). In some embodiments, the hollow fibers 444may be polymeric. In some cases, metallic fibers may be used within theheat exchanger 432. According to other embodiments, the heat exchanger432 includes a metal bellows or other structure comprising a substantialsurface area (e.g., fins) for facilitating heat transfer with the blood.In some embodiments, the hollow fibers 444 are hollow polyurethanefibers having an outer diameter between about 0.2 and 1.0 millimetersor, more specifically, between about 0.25 and 0.5 millimeters. Thehollow fibers may be woven into mats that can range from about 80 toabout 200 millimeters in width. In some embodiments, the mats are in acriss-cross configuration.

In some embodiments, a cylindrical shell 446 may be disposed between theheat exchanger 432 and the gas exchanger 434. In some embodiments, thecylindrical shell 446 may be considered as delineating or defining aboundary between the heat exchanger 432 and the gas exchanger 434. Insome embodiments, the cylindrical shell 446 prevents blood frommigrating between the heat exchanger 432 and the gas exchanger 434 otherthan in desired locations. In order to permit blood exiting the heatexchanger 432 to enter the gas exchanger 434, in some embodiments thecylindrical shell 432 includes one or more shell apertures 448.

In the illustrated embodiment, the one or more shell apertures 448 aredisposed near an end that is opposite that of the blood inlet 416. As aresult, blood entering the heat exchanger 432 from the blood inlet 416passes through at least a substantial portion of the heat exchanger 432before the blood can exit the heat exchanger 432 through the one or moreshell apertures 448 and into the gas exchanger 434.

In some embodiments the gas exchanger 434 may include a number ofmicroporous hollow fibers 450 through which a gas such as oxygen mayflow. The blood may flow around and past the hollow fibers 450. Due toconcentration gradients, oxygen may diffuse through the microporoushollow fibers 450 into the blood while carbon dioxide may diffuse intothe hollow fibers and out of the blood. In some embodiments, the hollowfibers 450 are made of polypropylene and have an outer diameter of about0.38 millimeters. According to other embodiments, the microporous hollowfibers have a diameter of between about 0.2 and 1.0 millimeters or, morespecifically, between about 0.25 and 0.5 millimeters. The hollow fibers450 may be woven into mats that can range from about 80 to about 200millimeters in width. In some embodiments, the mats are in a criss-crossconfiguration.

In some embodiments, as illustrated, the filter housing 414 defines afilter volume 452 between the filter housing 414 and the apparatushousing 412. A filter assembly 454, including a filter frame 456 and afilter net 458, divides the filter volume 452 into a first chamber 460that is defined at least in part between the filter assembly 454 and theapparatus housing 412 and a second chamber 462 that is defined at leastin part between the filter assembly 454 and the filter housing 414. Thefilter frame 456 may be formed of any desired material such as apolymer. In some embodiments, the filter net 458 is a polyester net or apolypropylene net. In some embodiments, at least portions of the filterassembly 454 may be coated with a biocompatible material. In someembodiments, the first purge port 428 is in fluid communication with thefirst chamber 460 and the second purge port 430 is in fluidcommunication with the second chamber 462.

In some embodiments, blood passing through the gas exchanger 434 passesthrough one or more openings 464 into the first chamber 460 of thefilter volume 452. At least some of the air bubbles, if any, within theblood may be purged through the first purge port 428. Blood may thenpass through the filter net 458 into the second chamber 462 of thefilter volume 452. Any air bubbles still within the blood may be purgedthrough the second purge port 430 before the blood exits the bloodprocessing unit 410 through the blood outlet 418.

The one or more openings 464 are best seen in FIG. 11. In someembodiments, as illustrated, the one or more openings 464 are disposedalong an arcuate path. While in FIG. 11, the arcuate path is shown asconcave relative to the end of the blood processing apparatus 410 atwhich the blood inlet 416 is located, in some embodiments the openings464 may instead curve in a convex relation to the end of the bloodprocessing apparatus 410. In some embodiments, the arcuate path mayinstead take a sinusoidal shape. The one or more openings 464 are sizedand positioned to permit a desired volume of blood flow through theblood processing apparatus 410.

The filter assembly 454 is best seen in FIG. 12. In some embodiments,the filter frame 456 includes a first annular frame ring 500 having afirst diameter and a second annular frame ring 502 having a seconddiameter that is greater than the first diameter. In some embodiments,as can be seen for example in FIG. 10, the filter housing 414 and thefilter assembly 454 may both be tapered, but may taper in oppositedirections. In some embodiments, tapering the filter assembly 454 canslow blood flow through the filter net 458 and can provide advantages inremoving air bubbles from the blood. In some embodiments, an oppositetaper in the filter housing 414 may further aid in bubble removal.

As shown in FIG. 12, the filter frame 456 includes one or more bridgeelements 504 that extend between the first annular frame ring 500 andthe second annular frame ring 502. The filter frame 456 also includesone or more arcuate ribs 506. By comparing FIGS. 11 and 12, it can beseen that the one or more arcuate ribs 506 are configured to align withthe one or more openings disposed within the apparatus housing 412 alongthe arcuate path 464. As a result, and as will be described with respectto FIGS. 13 and 14, this alignment can deflect or otherwise impact(e.g., reduce) blood flow velocity through the filter volume 452. Insome embodiments, if the path 464 is formed in a different shape thanthat illustrated, the one or more ribs 506 may be similarly shaped. Insome embodiments, the filter frame 456 also includes a plate portion 508that is arranged near the blood outlet 418 to limit preferential flow inthe area near the blood outlet 418.

In some embodiments, the filter frame 456 is configured to regulateblood flow velocity through the filter assembly 454. FIG. 13 is agraphical representation of blood flow velocity through a filter lackingthe filter frame 456 while FIG. 14 provides a graphical representationof blood flow velocity through the filter assembly 452. In both cases,the volumetric blood flow is quite similar, ranging from about 1.61 toabout 1.63 liters per minute. These computerized modeling results revealthat the filter frame 456 reduces the maximum blood flow velocitythrough the filter by as much as 65 percent, without negativelyimpacting the volumetric blood flow.

In some embodiments, backflow, or blood flowing backwards through thefilter assembly can be problematic. FIGS. 15 and 16 are relativefrequency density graphs, which show that backflow is reduced using thefilter frame assembly 454. In these graphs, the relative amount ofbackflow can be seen by comparing the relative frequency of negativevelocities with the relative frequency of positive velocities. Negativevelocities represent blood flowing backwards through the filter net 458while positive velocities represent blood flowing forwards, or in adesired direction, through the filter net 458.

In FIG. 15, which represents blood flow without the inventive filterframe assembly 454 and which corresponds to the velocity profile shownin FIG. 13, the total amount of backflow is about 51 percent of totalblood flow. In FIG. 16, which represents blood flow with the inventivefilter frame assembly 454 and which corresponds to the velocity profileshown in FIG. 14, the total amount of backflow is only about 16 percent.

Various modifications and additions can be made to the exemplaryembodiments discussed without departing from the scope of the presentinvention. For example, while the embodiments described above refer toparticular features, the scope of this invention also includesembodiments having different combinations of features and embodimentsthat do not include all of the above described features.

1. A blood processing apparatus comprising: an apparatus housing havinga blood inlet and a blood outlet, the blood inlet extending into aninterior of the apparatus housing; a heat exchanger disposed about theblood inlet and in fluid communication therewith; a gas exchangerdisposed about the heat exchanger and in fluid communication therewith;a filter housing coupled about the apparatus housing and defining afilter volume between the apparatus housing and the filter housing, thefilter volume in fluid communication with the gas exchanger via one ormore openings formed within the apparatus housing such that bloodexiting the gas exchanger can pass into the filter volume; and a filterassembly disposed within the filter housing, the filter assemblyincluding a filter frame having one or more ribs and a filter netdisposed on the filter frame, the one or more ribs aligned with at leasta portion of the one or more openings so as to reduce blood velocitythrough at least a portion of the filter net, wherein the filter framehas a first annular frame ring having a first diameter, a second annularframe ring having a second diameter greater than the first diameter andone or more bridge elements extending between the first annular framering and the second annular frame ring.
 2. The blood processingapparatus of claim 1, wherein the one or more openings comprise aplurality of openings arranged along an arcuate path, and the one ormore ribs comprise arcuate ribs aligned with the arcuate path.
 3. Theblood processing apparatus of claim 1, wherein the one or more ribs aredisposed between the first annular frame ring and the second annularframe ring.
 4. The blood processing apparatus of claim 1, wherein thefilter frame includes a plate portion arranged near the blood outlet tolimit preferential blood flow through the filter assembly near the bloodoutlet.
 5. The blood processing apparatus of claim 1, wherein the filterassembly divides the filter volume into a first chamber between thefilter assembly and the apparatus housing and a second chamber betweenthe filter assembly and the filter housing.
 6. The blood processingapparatus of claim 5, further comprising a first purge port in fluidcommunication with the first chamber and a second purge port in fluidcommunication with the second chamber.
 7. The blood processing apparatusof claim 6, wherein the filter housing has a frustoconical configurationhaving a smaller diameter at one end and a larger diameter at anopposing end, and the second purge port is located near the largerdiameter end of the filter housing.
 8. The blood processing apparatus ofclaim 7, wherein the first purge port is located near the smallerdiameter end of the filter housing.
 9. The blood processing apparatus ofclaim 6, wherein bubbles within the blood can exit through the firstpurge port and/or the second purge port.
 10. The blood processingapparatus of claim 1, wherein the gas exchanger is configured to permitgas to flow therethrough in order to add oxygen and remove carbondioxide from the blood passing through the gas exchanger.
 11. The bloodprocessing apparatus of claim 1, wherein the filter assembly includes abiocompatible coating on the filter net.
 12. The blood processingapparatus of claim 1, wherein the filter net comprises a polyesterfilter net or a polypropylene filter net.
 13. A blood processingapparatus comprising: an apparatus housing having a blood inlet and ablood outlet, the blood inlet extending into an interior of theapparatus housing; a heat exchanger core extending coaxially within theapparatus housing and axially aligned with the blood inlet; heatexchanger hollow fibers disposed about the heat exchanger core such thata heat exchanger fluid may flow through the heat exchanger hollow fibersand blood passing from the blood inlet may flow across the heatexchanger hollow fibers; a cylindrical shell extending coaxially aboutthe heat exchanger core, the cylindrical shell including an annularshell aperture disposed near an end of the cylindrical shell opposite toan end near the blood inlet, the annular shell aperture configured topermit blood to pass to an exterior of the cylindrical shell; gasexchanger hollow fibers disposed about the cylindrical shell such thatgases may flow through the gas exchanger hollow fibers and blood passingfrom the annular shell aperture may flow across the gas exchanger hollowfibers; a filter housing coupled about the apparatus housing anddefining a filter volume between the apparatus housing and the filterhousing, the filter volume in fluid communication with the gas exchangervia one or more openings formed within the apparatus housing along anarcuate path such that blood exiting the gas exchanger can pass into thefilter volume; a filter assembly disposed within the filter housing anddividing the filter volume into a first chamber between the filterassembly and the apparatus housing and a second chamber between thefilter assembly and the filter housing, the filter assembly including afilter frame having one or more arcuate ribs and a filter net disposedon the filter frame, the one or more arcuate ribs aligned with the oneor more openings along the arcuate path in order to slow blood velocitythrough the filter net, wherein the filter frame has a first annularframe ring having a first diameter, a second annular frame ring having asecond diameter greater than the first diameter and one or more bridgeelements extending between the first annular frame ring and the secondannular frame ring; a first purge port in fluid communication with thefirst chamber; and a second purge port in fluid communication with thesecond chamber.
 14. The blood processing apparatus of claim 13, whereinthe filter assembly includes a biocompatible coating on the filter net.15. The blood processing apparatus of claim 13, wherein the filter netcomprises a polyester filter net or a polypropylene filter net.
 16. Ablood processing apparatus comprising: an apparatus housing having ablood inlet and a blood outlet, the blood inlet extending into aninterior of the apparatus housing; a heat exchanger disposed about theblood inlet and in fluid communication therewith; a gas exchangerdisposed about the heat exchanger and in fluid communication therewith;a filter housing coupled about the apparatus housing and defining afilter volume between the apparatus housing and the filter housing, thefilter volume in fluid communication with the gas exchanger via one ormore openings formed within the apparatus housing such that bloodexiting the gas exchanger can pass into the filter volume wherein thefilter housing has a frustoconical configuration having a smallerdiameter at one end and a larger diameter at an opposing end; a filterassembly disposed within the filter housing, the filter assemblyincluding a filter frame having one or more ribs and a filter netdisposed on the filter frame, the one or more ribs aligned with at leasta portion of the one or more openings so as to reduce blood velocitythrough at least a portion of the filter net, wherein the filterassembly divides the filter volume into a first chamber between thefilter assembly and the apparatus housing and a second chamber betweenthe filter assembly and the filter housing; and a first purge port influid communication with the first chamber and a second purge port influid communication with the second chamber, wherein the second purgeport is located near the larger diameter end of the filter housing. 17.The blood processing apparatus of claim 16, wherein the one or moreopenings comprise a plurality of openings arranged along an arcuatepath, and the one or more ribs comprise arcuate ribs aligned with thearcuate path.
 18. The blood processing apparatus of claim 16, whereinthe filter frame has a first annular frame ring having a first diameter,a second annular frame ring having a diameter greater than the firstdiameter and one or more bridge elements extending between the firstannular frame ring and the second annular frame ring.
 19. The bloodprocessing apparatus of claim 16, wherein the filter frame includes aplate portion arranged near the blood outlet to limit preferential bloodflow through the filter assembly near the blood outlet.
 20. The bloodprocessing apparatus of claim 16, wherein the first purge port islocated near the smaller diameter end of the filter housing.
 21. Theblood processing apparatus of claim 16, wherein the gas exchanger isconfigured to permit gas to flow therethrough in order to add oxygen andremove carbon dioxide from the blood passing through the gas exchanger.22. The blood processing apparatus of claim 16, wherein the filter netcomprises a polyester filter net or a polypropylene filter net.